The present invention relates to loadings experienced by marine vessels, more particularly to methodologies for obtaining pressure loading predictions such as may be useful in the design of marine vessels.
Marine vessels (e.g., ships, small craft, high performance craft, etc.) are subjected to pressure loads induced by the sea. These pressure loads can be either of two types, viz., (i) a quasi-static pressure type load from the structure being below the water surface, or (ii) a slam-induced pressure load from a wave impacting on a part of the vessel. Historically, various algorithms have been developed to address both types of pressure loads, mainly using ship trial and model test data with some “engineering judgment” to arrive at pressure loads to be used for design. The design pressure is often a single value used to assess the adequacy of localized ship structure.
More recently, reliability and fatigue assessment methodologies have been developed for the design of global ship structures subjected to overall hull bending from wave action. These methodologies require the knowledge of the number of times that a given load will be experienced in the lifetime of the structure. For example, a peak design load may often be taken as the load that the structure might experience once in its lifetime. For loads that are less that the one cycle maximum, the structure will likely face these lesser loads more than once. Increasingly smaller loads will be experienced an increasing number of times during the life of the structure.
For ship structural components (e.g., metal plating, stiffeners, grillage, etc.), a similar process is needed to adequately assess the reliability and fatigue characteristics of the component. However, heretofore no method has existed to assess the cyclical nature of pressure loads on ship structural components due to wave slamming.